Discussion: Posterior urethral valves are the most common cause of bilateral hydronephrosis in a male infant. Affected infants may present with maternal oligohydramnios, pulmonary hypoplasia, and cystic renal dysplasia. Vesicourethral reflux tends to be unilateral and may lead to forniceal rupture and urinary ascites. Older children or adolescents may present with urinary tract infections, voiding difficulty, or end-stage renal disease. Type 1 valves are the most common and extend from the verumontanum distally, leaving a small opening posteriorly for the passage of urine. Voiding cystourethrogram is the test of choice for diagnosis. Treatment frequently involves early urinary diversion and subsequent valve ablation.